1. Field of the Invention
The subject invention pertains generally to test probes and, more specifically, to a new and improved integrated circuit (“IC”) test probe for use in various testing applications. Furthermore, the subject invention is capable of being employed in several different configurations that permit it to be used with a wide variety of IC chips.
An integrated circuit component must be tested and evaluated for reliability before actual use. For proper evaluation and testing, the IC must be electrically connected to a printed circuit board (“PCB”) by a reliable means. As the microelectronic field has advanced, the complexity and concentration of components in an IC has increased dramatically. This increase has led to an increased lead density of the IC chip with a corresponding decrease in the gap between the leads. As a result, there is a need for smaller sized test probes to accommodate these increasingly complex ICs.
It should also be noted that ball grid array (“BGA”) and land grid array (“LGA”) packages have become increasingly popular because of their high densities and low profiles. With a BGA package, the rounded solder balls of the BGA are usually soldered directly to a corresponding surface mount pad of a printed circuit board, rather than the pins of a pin grid array IC package.
2. Description of the Related Art
Applicant's U.S. Pat. No. 6,844,749 entitled “Integrated Circuit Test Probe” which issued on Jan. 18, 2005 and is assigned to the same assignee of the subject invention provides a new and improved test probe small enough to accommodate the increased density of leads on modern IC chips. U.S. Pat. No. 6,844,749 also provides a test probe that has durable and flexible contacts for connecting a component to a PCB. Still further, applicant's prior patent provides a test probe that is capable of accepting ball grid array (“BGA”) or land grid array (“LGA”) chips.
Although the integrated circuit test probe of applicant's U.S. Pat. No. 6,844,749 fulfills a need for connecting a plurality of leads on modern IC chips, it has been found that certain customers mishandle the test probe of said patent.
More particularly, U.S. Pat. No. 6,844,749 discloses a test probe consisting of an elongated screw machine contact biased by a helical spring and mounted in a through hole of a non-conductive substrate. One end of the contact includes a crown for engaging a solder ball lead of an IC package, and the contact includes an intermediate collar which maintains the contact within the through hole. The helical spring is disposed about the contact, with one end thereof engaging the lower end of the collar. The other end of the helical spring has contiguous coils and is of a reduced diameter so as to extend beyond the lower end surface of the non-conductive substrate to make electrical contact with a printed circuit board. When the test probe of U.S. Pat. No. 6,844,749 is compressed between an IC package and a printed circuit board, the inherent twisting of the helical spring causes the contact to tilt and make electrical contact with the contiguous coils, thereby establishing a direct electrical path between the IC package and the printed circuit board, with minimum resistance and minimum inductance. The disclosure of U.S. Pat. No. 6,844,749 is incorporated by reference in this application in its entirety.
The contiguous coils of the helical spring which extend beyond the lower end of the non-conductive substrate to make electrical contact with a printed circuit board are exposed and subject to mishandling or twisting by the operator during mounting of the integrated circuit test probe in a fixture. The contiguous coil ends of the helical spring are of very small diameter and cannot readily absorb any unintended force, whereby one or several helical springs may be twisted so as to render the integrated test probe inoperative.
It is an object of the subject invention to provide an improved integrated circuit test probe of the type disclosed in U.S. Pat. No. 6,844,749, but with an arrangement wherein the lower end of the contact is not subjected to damage should an inadvertent force be applied to the lower ends of the contact.